Folding back-hitch gantry



Dec. 14, 1965 c. NOLL ETAL FOLDING BACK-HITCH GANTRY 2 Sheets-Sheet 1 Filed Dec. 20, 1962 INVENTORS GEORGE C. NOLL BY JOHN D. NIELSEN 6/ (NW6 ATTORNEYS Dec. 14, 1965 G. c. NOLL ETAL 3,223,250

FOLDING BACK-HITCH GANTRY Filed Dec. 20, 1962 2 Sheets-Sheet 2 INVENTORS GEORGE C. NOLL JOHN D. NlELSEN 6W mMWwm ATTORNEYS United States Patent Ofifice 3,223,250 Patented Dec. 14, 1965 3,223,250 FGLDING BACK-HITCH GANTRY George C. Noll, Elyria, and John D. Nielsen, Lorain, Ohio, assignors, by mesne assignments, to Koehring Company, Milwaukee, Wis., a corporation of Wisconsin Filed Dec. 20, 1962, Ser. No. 246,206 Claims. (Cl. 21259) This invention relates generally, as indicated, to a back-hitch gantry and more particularly to a folding back-hitch gantry for power cranes, shovels, and the like.

In such power cranes and shovels, a boom is pivoted to a revolving superstructure and is raised and lowered by means of a reeving system which is anchored at a point on such superstructure. It is, of course, desirable to have this anchor point as high as possible on the superstructure to obtain as great an angle as possible between the derricking cable and the crane or shovel boom. This increases the raising moment acting on the boom and, of course, the load supported thereby. It will be understood that the greater the moment, the greater the lifting capacity.

It is prevalent practice to mount power cranes on wheeled carriers for highway travel and for added mobility in moving from one place to another on the job. If, for highway travel, the anchor point for the boom hoist cable sheaves is as high as desired to obtain the required lifting capacity, or indeed, to raise the boom from horizontal position, such presents an obstruction in that the crane cannot readily pass under bridges, power lines, or the like. Fixed gantry structures for the dern'cking sheave anchors have been provided, but these are impracticable and undesirable since it is required to remove entirely or dismount such anchor before the crane can be transported. For smaller capacity cranes, telescoping back-hitch gantries have been provided and reference may be had to the copending application of George C. Noll and Paul E. Wesebaum, entitled Back-Hitch Gantry, Serial No. 103,045, filed April 14, 1961 and now Patent No. 3,092,260. However, with such telescoping gantries, the desired height for larger capacities is not obtainable and it is sometimes difiicult to erect the gantry without outside assistance. Moreover, during such erection, the parts of the gantry must actually be disconnected and reset in another position.

It is accordingly a principal object of the present invention to provide a back-hitch gantry which will obtain greater height in its erected position.

A further principal object is the provision of a folding back-hitch gantry for power cranes and the like which can easily be erected and lowered.

Another object is the provision of a folding back-hitch gantry for cranes which can be used alternatively either in its lowered or elevated position.

Still another object is the provision of a folding backhitch gantry which will maintain the derricking for the boom always connected to the superstructure.

Other objects and advantages of the present invention will become apparent as the following description proceeds.

To the accomplishment of the foregoing and related ends, the invention, then, comprises the features hereinafter fully described and particularly pointed out in the claims, the following description and the annexed drawings setting forth in detail a certain illustrative embodiment of the invention, this being indicative, however, of but one of the various ways in which the principle of the invention may be employed.

In said annexed drawings:

FIG. 1 is a fragmentary side elevation of the superstructure of a crane in accordance with the present invention with the back-hitch gantry shown in its retracted folded position;

FIG. 2 is a top plan view of the gantry alone as seen in FIG. 1;

FIG. 3 is a fragmentary side elevation similar to FIG. 1 illustrating the gantry in its elevated position;

FIG. 4 is an enlarged fragmentary horizontal section taken substantially on line 44 of FIG. 1;

FIG. 5 is a fragmentary section taken through the hinge and locking pins of such back-hitch gantry on the line 55 of FIG. 3; and

FIG. 6 is an enlarged fragmentary vertical section of the harness taken substantially on the line 66 of FIG. 2.

Referring now to the drawings and more particularly to FIG. 1, there is illustrated the basic framing of a power driven crane superstructure. Such superstructure may be rotatably mounted on a turntable 1 supported on a carrier frame bed 2 which is preferably of the mobile type provided with an independent prime mover and steerable ground engaging rubber tired wheels. Reference may be had to the aforementioned Noll et al. application for a disclosure of such a carrier. The superstructure includes a turntable bed or base 3 which is provided at the front or forward end with projecting members 4 providing a pivot 5 for the foot of a boom 6 which is thus pivotally mounted on the turntable bed for elevation about such pivot. Also mounted on the turntable bed 3 is an A-frame shown generally at 7 which includes columnar members 8, front inclined frame members 9 and rearward'ly inclined frame members 10 which are connected to the top of the columnar frame 8 at 11 and 12, respectively. The columns 8 are interconnected at the peak of the A-frame by means of an A-frarne pin 13.

A rear deck 15 is pivotally connected at 16 to the rear of the turntable bed 3 and is supported in such horizontal position by the rear inclined A-frame members 10. At the rear of such rear deck is a counterweight 17 which will help counterbalance the forces exerted upon the turntable bearing 1. A prime mover will generally be mounted on the rear deck 15 driving a dual drum boom hoist and dual load hoist drum mounted on the turntable bed 3 and column 8 for raising and lowering the boom 6 and the load supported thereby, respectively. The various shafts for the drive may be mounted in the semicircular cut-out portions of the A-frame columnar members 8 as illustrated.

Secured to the back of the frame thus provided adjacent to the counterweight 17 are two vertically extending relatively heavy struts 20 and 21, which are transversely spaced. Such struts are rigidly secured to the frame and extend upwardly approximately to the height of the peak of the A-frame. Pivotally connected to the top of each such strut by means of a pin 22 is a pair of bell-crank gantry links 23 and 24, with each such link 8 including a relatively long portion 25 and a relatively short offset portion 26. Each such pair of bell-crank gantry links is pivotally connected by means of a pin 27 at the elbow thereof or the juncture between the portions 25 and 26 to gantry links 28 and 29. The upper ends of such gantry links 28 and 29 are interconnected by means of an elongated gantry pin 30. The gantry links 28 and 29 then pivotally interconnect the pins 27 at the elbow of the bell-crank gantry links 23 and 24 and the outer ends of the gantry pin 30.

In FIG. 1, the back-hitch gantry is shown in its folded or retracted position and such links 28 and 29 constitute a linear continuation of the relatively short offset portions 26 of the bell-crank links 23 and 24. The distal ends of such relatively short portions 26 of such bellcrank links is provided with aligned pin apertures to receive a locking pin 32. Such pin holes are aligned with pin holes in the struts and 21 so that the pins 32 may be employed to lock the outer ends of the offset portions 26 to the struts 20 and 21 as shown in FIG. 1. The gantry pin is thus shown in its lowered position, but in such position is still firmly connected to the frame struts 20 and 21 through the Igantry links 28 and 29 and the offset portions 26 of the bell-crank links. In such position, the gantry pin 30, which is the anchor of the boom hoisting mechanism, will be sufficiently low to clear wires, bridges, etc. for highway travel of the crane. In such lowered position, the gantry pin may also serve for elevating the boom.

To raise and lower the boom, a boom hoist cable will normally be trained about sheaves in a floating harness which is connected to boom pendants which in turn are connected to the peak of the boom 6. Such cable is also trained about a harness which is connected by pins 41 and 42 to harness straps 43 and 44, respectively. As shown in FIG. 6, such harness 48 comprises upper and lower plates 46 and 47 through which headed sheave axles 48 extend held in place by keepers 49. Sheaves 59, 5'1, 52, and 53 are mounted on such horizontally spaced sheave axles with sheave bushings 55 being provided which are held to such sheaves by dowel pins 56. Grease fittings 57 may also be provided to ensure proper lubrication of such sheaves. The boom hoist cable may then be trained back and forth between the sheaves of the floating harness and the harness 40 to obtain a considerable mechanical advantage for the elevation of the boom 6. The straps 43 and 44, as shown in FIG. 2, are each comprised of parallel strap members which are connected at the proximal end by members 59 and 60, respectively. As shown in FIG. 4, each of the members 59 and 60 is provided with an aperture With collars 61 and 62 being secured adjacent such apertures to provide an elongated hub which is in turn mounted on a bushing 63 held to such hub by a dowel pin 64. A grease fitting 65 is provided ensuring free rotation of the members 59 and 60 and thus the straps 43 and 44 on the gantry pin 30. The anchor ends of the straps 43 and 44 are thus pivotally connected to the gantry pin 30 and the distal ends of such straps are pin connected to the harness 40 which is in turn connected by the boom derricking system to a floating harness, to the boom pendants, and to the peak of the boom 6. When the crane boom is dismantled and the crane is moving to or from a job site, the struts 43 and 44 will lie substantially horizontally supported between the gantry pin 30 and the top of the A-frame pin 13. In this position, the gantry pin 30 and the struts 43 and 44 will readily clear bridges, overhead wires, and like highway obstructions.

Also pivotally connected to the gantry pin 30 is a gantry strut shown generally at 70. The gantry strut 70, which is comprised of tubular strut members 71 and 72 interconnected by diagonal lacing members 73 and 74, pivotally connects the gantry pin 30 with the A-frame pin 13. As shown in FIGS. 2 and 4, the ends of the strut members 71 and 72 are bifurcated, as shown at 75 and 76 for the strut 72, to straddle the gantry links 28 and 29. A transverse tubular lacing member 78 is also provided extending between the struts 71 and 72 and such is provided with upstanding projections 79 and 80 which laterally confine the straps 43 and 44 when the straps are in their horizontal or traveling position. The gantry strut frame 70 is principally a compression member whereas the other members of the back-hitch gantry are principally tension members.

Reading from bottom to top in FIG. 4, it will be seen that the following elements are mounted on the outer ends of the gantry pin 30:

A locking collar 82 held by pin 83;

End portion 76 of the strut 72;

Gantry link 28;

End portion 75 of the strut 72;

The hub for the projecting member 60 of the strap 44 comprised of the collar 61, member 60 and collar 62; and

Collar 84 held adjustably in place by a set screw 85 and jamb nut 86.

The opposite end of the gantry pin 30 will be allochirally identical in form with the bifurcated end of the strut 71 straddling the gantry link 29.

Referring now to FIGS. 3 and 5, in order to elevate the back-hitch gantry to its raised position, with the boom derricking system connected and the boom extending approximately horizontally in front of the machine on the ground, the pin 32 is removed and the boom hoist clutch is engaged as if to elevate the boom. However, since the back-hitch gantry has now been unlocked, instead of the boom initially being elevated, the back-hitch gantry will now be unfolded moving into its elevated position as depicted in FIG. 3. The pull on the derricking cable trained about the sheaves 50 through 53 will pivot the gantry strut 7 0 about the A-frame pin 13 elevating the gantry pin 36 unfolding the links 23, 24-28 or 29 about their point of pivotal interconnection viz, pin 27. Such unfolding will continue until the links 28 and 29 are linear continuations of the elongated major portions 25 of the bellcrank links 23, 24. This position is shown in FIG. 3. The back-hitch gantry Will remain in the elevated position shown in FIG. 3 as long as there is sufficient pull on the derricking cable trained about such sheaves 50 through 53 to hold the gantry up. As soon as the gantry reaches the FIG. 3 position, the boom 6 will start to elevate, and the weight of the boom will hold the gantry thus erected. However, should the derricking cable become slack, the gantry may then tend to collapse to its folded condition shown in FIG. 1.

To lock the gantry in its elevated position, the gantry links 28 and 29 are provided with offset eye portions adjacent the lower ends thereof as shown in FIGS. 1 and 3. These eyes are provided with pin holes 91 which are spaced from the pin holes in the lower ends of such links 28 and 29 a distance equal to the distance between pins 27 and 32 in the locked position of the gantry shown in FIG. 1. In this manner, the pin holes in the outer ends of the offset portions 26 of the links 23 and 24 will become aligned with the pin holes 91 in the eyes 90 when the gantry links move to the position shown in FIG. 3. The pin 32, which had previously been removed to permit elevation of the gantry, can now be inserted again through the distal ends of the offset portions 26 of the links 23 and 24 and through the holes 91 in the eyes 90 at the lower ends of the links 28 and 29. With the pin 32 thus positioned as shown in FIG. 3, the backhitch gantry will be locked in its erected position and cannot collapse or fold. The gantry pin 30 is accordingly considerably more elevated in the raised position of the gantry than in the lowered position as shown in FIG. 1.

In the illustrated embodiment, the height of the anchor or gantry pin 30 can be increased by approximately nine feet. This has been found especially helpful in the initial elevation of very long booms in that the raising moment acting on such booms will proportionately be measured by the height of the gantry pin 30 above the boom foot pivot 5. Also, through the boom normal operating ranges, the raising moment acting on the boom will be greatly increased due to the rearward displacement of the gantry pin 30 from the boom axis. It has been found with such folding back-hitch gantry that the height obtainable is greatly increased due to the addition of the lengths of the links 28 and the longer portion 25 of the links 23, 24 to the vertical height of the pin 22. Accordingly, a higher anchor for the boom derricking system is provided with still a very low clearance also being provided in the folded or retracted position for highway clearances.

Although the operator will normally remove pin 32 and then engage the boom hoist clutch to elevate the gantry to its FIG. 3 position and then replace the pin 32 in the eyes 90, it will be readily understood that the replacement of the pin may be accomplished by an automatic pin locking mechanism carried on the outer ends of the offset portions 26 of the bell-crank links 23, 24 in much the same manner as shown in the aforementioned copending application of Noll et al. In this manner, the releasing and setting of the pins 32 can then be accomplished Without the operator leaving the cab and in a very, very short time.

Other modes of applying the principle of the invention may be employed, change being made as regards the details described, provided the features stated in any of the following claims or the equivalent of such be employed.

We, therefore, particularly point out and distinctly claim as our invention:

1. A back-hitch gantry for cranes and the like having an A-frame superstructure comprising, a frame pivoted to the peak of said A-frame, a gantry pin at the distal end of said frame, a vertically extending strut at the back of said superstructure, a folding linkage interconnecting the top of said strut and said gantry pin, said folding linkage including a first link pivoted to said pin, a second link pivoted to said first link and to the top of said strut, said second link including a relatively short offset portion extending beyond the pivotal connection of said first and second links, and means to lock said offset portion to said strut to hold said linkage in folded condition and said gantry pin in lowered position with said oflFset portion in alignment with said first link.

2. A back-hitch gantry as set forth in claim 1 wherein said first link also includes a relatively short offset portion adjacent the pivotal connection between said first and second links, and said lock means is also operative alternately to lock said offset portions together to hold said linkage in unfolded condition and said gantry pin in elevated position with said first and second links in alignment.

3. A back-hitch gantry for cranes and the like having an A-frame superstructure comprising, a frame pivoted to the peak of said A-frame, a gantry pin at the distal end of said frame, a vertically extending strut at the back of said superstructure, a folding linkage interconnecting the top of said strut and said gantry in including a first link pivoted to said pin, a second link pivoted to said first link and to the top of said strut, said second link including a relatively short offset portion extending beyond the pivotal connection of said first and second links, said first link including a laterally oifset portion, and means to lock said ofiset portions together to hold said linkage in unfolded condition and said pin in elevated position.

4. In a crane having a revolving superstructure including an A-frame, a boom pivoted to the front of said superstructure, a strut frame pivoted to the peak of said A- frame, a gantry pin mounted at the distal end of said strut frame adapted to serve as an anchor for raising and lowering said boom, and a folding linkage interconnecting said gantry pin and the rear of said revolving superstructure, said linkage including a first link pivoted to said gantry pin, a second link in the shape of a bellcrank, said first link being pivoted to said second link intermediate its ends to provide an offset portion extending beyond the pivotal connection between said links, the end of said second link remote from said oifset portion being pivoted to said superstructure, and locking pin means operative alternately to pin-lock said offset portion to said first link to hold said gantry pin in elevated position or to said superstructure to hold said gantry pin in lowered position.

5. A crane as set forth in claim 4 including an offset portion on said first link, said locking pin means being operative to pin-lock said offset portions on said first and second links together to hold said gantry pin in raised position as aforesaid.

References Cited by the Examiner UNITED STATES PATENTS 2,411,305 11/1946 Taylor et a1. 21259 2,795,338 6/1957 Blanchard et al 212-59 SAMUEL COLEMAN, Primary Examiner.

KARL J. ALBRECHT, Examiner. 

1. A BACK-HITCH GANTRY FOR CRANES AND THE LIKE HAVING AN A-FRAME SUPERSTRUCTURE COMPRISING, A FRAME PIVOTED TO THE PEAK OF SAID A-FRAME, A GANTRY PIN AT THE DISTAL END OF SAID FRAME, A VERTICALLY EXTENDING STRUT AT THE BACK OF SAID SUPERSTRUCTURE, A FOLDING LINKAGE INTERCONNECTING THE TOP OF SAID STRUT AND SAID GANTRY PIN, SAID FOLDING LINKAGE INCLUDING A FIRST LING PIVOTED TO SAID PIN, A SECOND LINK PIVOTED TO SAID FIRST LINK AND TO THE TOP OF SAID STRUT, SAID SECOND LINK INCLUDING A RELATIVELY SHORT OFFSET PORTION EXTENDING BEYOND THE PIVOTAL CONNECTION OF SAID FIRST AND SECOND LINKS, AND MEANS TO LOCK SAID OFFSET PORTION TO SAID STRUT TO HOLD SAID LINKAGE IN FOLDED CONDITION AND SAID GANTRY PIN IN LOWERED POSITION WITH SAID OFFSET PORTION IN ALIGNMENT WITH SAID FIRST LINK. 